1. Field of the Invention
The present invention pertains to components such as integrated circuits, systems including such components, and power supplies therefore. More particularly, the present invention pertains to the use of a power consumption signal and compensation circuitry to adjust the voltage supplied to a system or a component.
2. Description of Related Art
Proper operation of most electronic devices typically requires power supplies to maintain voltage levels within certain specifications. However, modern electronic devices often achieve power savings by providing power to various components or portions of such components only when needed. Such power saving techniques result in large and rapid changes in power demand as significant portions of the system may be enabled and disabled in time periods on the order of one clock period of a high frequency logic clock in the system. Consequently, modem power delivery systems need to be capable of adapting to large and rapid current changes.
A simple model of a traditional voltage supply includes a voltage source, an equivalent series inductance (ESL) in series with the voltage supply, and an equivalent series resistance (ESR) in series with a capacitor that is parallel to the voltage supply. The ESL and ESR components reflect the reality that no power supply can instantaneously respond to every possible change in load. When a dramatic decrease in current demand occurs, the ESL effectively continues driving current through the load, thus causing a voltage bounce. Similarly, when a large increase in current demand occurs, the ESR resists the immediate increase in current, causing a voltage droop. The output voltage returns to a steady state in a period determined mostly by the ESL and ESR values.
According to traditional techniques, a voltage supply may be kept within an acceptable range by utilizing components which provide a smaller ESL and a smaller ESR. The power supply itself may be changed and/or other techniques may be used, such as distributing capacitors throughout the system. Such techniques typically increase the bulk of the power supply or the overall system (e.g., in the case where capacitors are added). Increasing the overall size of the power distribution network exacerbates the difficulty of controlling the voltage at a component because the overall impedance of the power delivery system is altered by the enlarged network, usually resulting in a degraded response time to load changes. Accordingly, network altering techniques are somewhat self defeating because the changes to the power supply network necessitate further compensating improvements.
Another prior art approach to reducing power supply swings involves actively adjusting the power supply (see, e.g., U.S. Pat. No. 5,945,817). This prior art technique utilizes a power indicator signal from a component to adjust the voltage output from the power supply. The power supply increases the voltage when the component switches to a lower power mode (anticipating an increase in power consumption) and decreases the power supply when the component switches to a higher power mode (anticipating a decrease in power consumption). In this manner, the power supply makes pre-emptive adjustments that may reduce an expected range of voltages supplied to the component.
Such a pre-emptive adjustment approach may not be optimal, however, for all systems. Using such an approach, there is no attempt to maintain a constant voltage supply output value. Additionally, such a system does not necessarily consider the xe2x80x9ctransfer functionxe2x80x9d that is inherent in the particular power supply of every electronic system. This transfer function is the complex impedance between the source and the load, and it affects the ability of the power supply to deliver the desired voltage to the load. Prior art approaches fail to adequately consider the effects of the power supply transfer function of the system in conjunction with power consumption hints in adjusting voltages supplied to a system.